What could lead to a decrease in pH in an anaerobic digester?

A decrease in pH in an anaerobic digester can occur due to the oxidation of hydrogen sulfide to sulfuric acid. This process involves hydrogen sulfide, a common byproduct of anaerobic digestion, being converted into sulfuric acid, which is a strong acid. When sulfuric acid is produced, it dissociates in water, releasing hydrogen ions and causing a decrease in pH since pH is a measure of the concentration of hydrogen ions in solution.

In the context of an anaerobic digester, maintaining a balanced pH is crucial for microbial activity. Most of the beneficial microorganisms in the digester operate best within a certain pH range. A significant drop in pH due to the production of sulfuric acid can inhibit these organisms and compromise the digestion process.

The other factors listed in the alternatives can influence the operational efficiency of a digester, but they do not result in a direct decrease in pH. For example, an increase in alkalinity would typically buffer pH levels, helping to stabilize them rather than decrease them. Similarly, a decrease in sludge volume may not have a direct correlation with pH changes, and increased temperature, while it can influence microbial activity and gas production rates, does not directly cause